1. Field of the Invention
The present invention relates to an endoscope system, a processor device, and a method for operating an endoscope system, for imaging an observation object in a patient.
2. Description Related to the Prior Art
In a medical field, it is common to image an observation object (for example gastrointestinal mucous membranes) in a patient, and observe the image for a diagnosis. An endoscope system comprises a light source device for generating illumination light to irradiate an observation object, an endoscope having an insertion section for being inserted in a patient and imaging the observation object with use of an image sensor provided in a distal portion of the insertion section, and a processor device for generating an image of the observation object based on image signals which the image sensor outputs and displaying the image on a monitor.
The image sensor for imaging the observation object is for example a color image sensor which includes a blue pixel (hereinafter referred to as the B pixel) for receiving light in a blue wavelength band, a green (hereinafter referred to as the G pixel) for receiving light in a green wavelength band, and a red pixel (hereinafter referred to as the R pixel) for receiving light in a red wavelength band. Recently, it is known an endoscope system using a color image sensor that includes the B pixel, G pixel, and R pixel of three primary colors, and a fourth color pixel whose spectral characteristic is different from that of the BGR pixels. For example, they are known an endoscope system equipped with a color image sensor which includes the BGR pixels, and a pixel for receiving light in a blue wavelength band which is narrower than the wavelength band of the light received by the B pixel, and an endoscope system equipped with a color image sensor which further includes a pixel for receiving light in a green wavelength band which is narrower than the wavelength band of the light received by the G pixel (United States Patent Application Publication No. 2012/154565 corresponding to Japanese Patent Laid-Open Publication No. 2012-125462). In addition, it is known an endoscope system which includes an image sensor having the BGR pixels and a pixel to receive near infrared light (United States Patent Application Publication No. 2011/063427 corresponding to Japanese Patent Laid-Open Publication No. 2013-163027).
Further, it is known a color image sensor that has the BGR pixels and a white color pixel (hereinafter referred to as the W pixel) which receives each light in a blue wavelength band, a green wavelength band and a red wavelength band (Japanese Patent No. 5141757). The color image sensor having the W pixel is used for digital cameras to image a person or scenery.
In case an observation object is imaged by the endoscope system, a distance between the distal portion of the insertion section where the image sensor is mounted and the observation object, that is, a distance between the image sensor and the observation object which the image sensor images (hereinafter referred to as the imaging distance) varies according to how a doctor using the endoscope system observes the observation object.
For example, in case running patterns of blood vessels or microstructures such as pit patterns on a surface (or a vicinity of a surface) of the observation object are observed, the distal portion of the insertion section is brought close to the observation object so as to greatly observe the running patterns of the blood vessels or the pit patterns. Accordingly, in case the distal portion of the insertion section is brought close to the observation object (the imaging distance is short), the endoscope system is expected to offer an image in which the running patterns of the blood vessels or the pit patterns can be easily observed.
On the other hand, for searching a lesion part, the distal portion of the insertion section is kept away from the observation object to observe digestive organs generally from a remote place. Accordingly, in case the distal portion of the insertion section is kept away from the observation object (the imaging distance is long), the endoscope system is expected to offer an image in which it is easy to discover lesions in a distant view.